OPTICAL AXIS ADJUSTMENT DEVICE

An optical axis adjustment device for a headlamp unit to be mounted in a vehicle is configured to adjust an optical axis of the headlamp unit. the optical axis adjustment device includes an engine temperature acquirer, a displacement amount calculator, an operation information acquirer, and an optical axis adjuster. The engine temperature is configured to acquirer acquire a temperature in an engine compartment of the vehicle. The displacement amount calculator is configured to calculate a displacement amount of the optical axis on a basis of the temperature. The operation information acquirer is configured to acquire operation information indicating an operation status of a cooling device for the engine. The optical axis adjuster is configured to adjust the optical axis of the headlamp unit on a basis of the displacement amount and the operation information.